1. Field of the Invention
The present invention relates to a sticker, a method of producing the same, and a sticker printing method. More particularly, the present invention relates to a sticker having a first surface as a medium of digital hard copy and a second surface operating as an adhesive surface, a method of producing the same, and a sticker printing method in which the sticker is used.
2. Description Related to the Prior Art
There is an automatic portrait producing machine with a trade name of "Print Club" recently popular to teenagers. The machine has a height sightly greater than an average height of human beings, and incorporates a pick-up device, a display and a color printer. When a client stands in front of the machine and inserts coins, his or her human face is picked up and indicated by the display. Then he or she selects one of preset designs for the background of a frame, and then pushes a print button. Finally a combined image including the human face and the background design is printed on sticker material.
The term "sticker material" is herein used to represent a sheet material which has a recording surface and a back surface, and in which the recording surface is adapted to record an image according to image data of an object being picked up, and the back surface is provided with adhesive agent for the purpose of easily enjoying the digital hard copy of the image.
A sticker sheet has an adhesive layer with which the back surface of the recording medium is coated. Release paper is placed on the adhesive layer in a peelable manner. In FIG. 13, a sticker sheet 2 has cut lines 3 each of which is rectangularly shaped. The sticker sheet 2 is partitioned by the cut lines 3 into the a plurality of sticker chips 4. The sticker chips 4 have a size of 17.times.23 mm, and are arranged in a matrix.
A common combined image is equally recorded to any of the sticker chips 4. After the printing the sticker chips 4 are peeled along the cut lines 3. As the sticker chips 4 have adhesive layer disposed on the back surface, the sticker chips 4 can be attached to a notebook or the like very easily.
There are various types of full-color printing, including a sublimation type of thermal transfer recording method, and a direct thermal recording method disclosed in U.S. Pat. No. 4,734,704 (corresponding to JP-A 61-213169). In the thermal transfer recording method, a thermal transfer recording sheet is used. Ink ribbon is overlaid on the thermal transfer recording sheet. A thermal head applies heat to the rear of the ink ribbon, to transfer dye of the ink ribbon to a dye receiving layer of the recording sheet. In the direct thermal recording method, a thermosensitive recording sheet is used. A thermal head applies heat to the recording sheet to develop colors for recording an image.
FIG. 10 illustrates a layered structure of a sticker sheet 5 of a thermosensitive recording material. A thermosensitive recording sheet 11 is constituted by a support 6 and coloring layers 10 disposed to overlie thereon. The support 6 is constituted by support paper 7 and laminate layers 8 and 9 disposed on respective surfaces of the support paper 7. The coloring layers 10 are disposed on the obverse laminate layer 8. Release paper 13 is adhered to the reverse laminate layer 9 of the support 6 by use of adhesive layer 12. There are cut lines 14 cut through a range from the coloring layers 10 to the adhesive layer 12, to divide the recording sheet 11 into sticker chips.
If the recording is monochromatic, the sticker sheet 5 has only one thermosensitive coloring layer. For full-color recording, the coloring layers 10 include yellow, magenta and cyan thermosensitive coloring layers in sequence toward the support paper. To color the coloring layers selectively, the coloring layers are different in sensitivity to heat. The cyan coloring layer lying in the deepest position has the lowest sensitivity and requires the highest heat energy for developing certain color density. The yellow coloring layer lying in the least deep position has the highest sensitivity and requires the lowest heat energy for developing certain color density. The yellow and magenta coloring layers are provided with optical fixability to ultraviolet rays. For the full-color recording, each heated coloring layer directly overlying on a coloring layer as a present target must be prevented from being colored again. Thus the yellow and magenta coloring layers are fixed with ultraviolet rays of predetermined wavelength ranges for destroying coloring ability.
FIG. 11 illustrates a layered structure of a sticker sheet of a sublimation type of thermal transfer recording material. A thermal transfer recording sheet 19 is constituted by a support 15 and a dye receiving layer 18 disposed to overlie thereon. The support 15 is constituted by support paper 16 and a reverse laminate layer 17 disposed on a back surface of the support paper 16. Release paper 21 is adhered to the reverse laminate layer 17 of the support 15 by use of adhesive layer 20. There are cut lines 22 cut through a range from the dye receiving layer 18 to the adhesive layer 20, to divide the thermal transfer recording sheet 19 into sticker chips.
The sticker sheet is passed between the thermal head and a platen roller in the course of printing. In FIG. 12, a heating element array 26 of a thermal head 25 is offset from a center of a platen roller 27. When a portion where some of the cut lines are aligned is conveyed past the platen roller 27, the sticker sheet 5 is likely to be pressed toward the release paper. Then the cut lines 14 are likely to bend and open in the position of the broken line A of FIG. 13. The rigidity of the sticker sheet 5 changes, to change the pressing force of the heating element array 26. There occurs irregularity in density in an image printed on the sticker chips 4.
During the conveyance for printing, the sticker sheet is likely to bend in a direction toward the release paper. The cut lines are likely to be rubbed. It is likely that the sticker chips are incidentally peeled without intention.